/*
 * Copyright (C) 2020 HERE Europe B.V.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 * License-Filename: LICENSE
 */

package org.ossreviewtoolkit.utils.spdx.model

/**
 * Specifies checksum value and algorithm.
 */
data class SpdxChecksum(
    /**
     * The checksum algorithm.
     */
    val algorithm: Algorithm,

    /**
     * The lower case hexadecimal checksum value.
     */
    val checksumValue: String
) {
    companion object {
        internal val HEX_SYMBOLS_REGEX = "^[0-9a-f]+$".toRegex()
    }

    enum class Algorithm(val checksumHexDigits: Int) {
        MD2(32),
        MD4(32),
        MD5(32),
        MD6(-1),
        SHA1(40),
        SHA224(56),
        SHA256(64),
        SHA384(96),
        SHA512(128);
    }

    init {
        require(checksumValue.isNotBlank()) { "The checksum value must not be blank." }

        require(checksumValue.matches(HEX_SYMBOLS_REGEX)) {
            "The checksum value must only contain lower case hexadecimal symbols."
        }

        require(algorithm.checksumHexDigits == -1 || checksumValue.length == algorithm.checksumHexDigits) {
            "Expected a checksum value with ${algorithm.checksumHexDigits} hexadecimal symbols, but found " +
                    "${checksumValue.length}."
        }
    }
}
